Currently, extensions to the LTE Release 8 standard are discussed for future releases, like LTE Release 9 or IMT (international mobile telephony) advanced/LTE-Advanced, e.g. in order to increase system performance.
At the same time, there may be different application scenarios for LTE systems in different frequency bands. Specifically, the tight cooperation of LTE with GSM (global system for mobile communications) transmissions may be considered as such a cooperation allows for providing full coverage GSM systems in combination with high performance LTE radio air interfaces.
For example, as the minimum LTE bandwidth may be 1.4 MHz in a system, it will be difficult to accommodate e.g. an additional GSM carrier of 200 KHz bandwidth in this same frequency band of 1.6 MHz, as there will be strong frequency guard bands required to avoid inter system interference.
However, if a GSM carrier and an LTE carrier are used in close-by frequency bands or even in the same frequency band, there may be strong interference due to mutual out-of-band emissions. As GSM has a much smaller bandwidth of only 200 KHz compared to e.g. 10 or 20 MHz for LTE, the main interference may stem from GSM to the LTE system under the assumption that both carriers have substantially the same overall transmit power.
In consideration of the above, it is an object of examples of the present invention to overcome one or more of the above drawbacks. In particular, the present invention provides methods, apparatuses, a system and a related computer program product for signal transmission and reception.
According to an example of the present invention, in a first aspect, this object is for example achieved by a method comprising:
accommodating, in frequency domain, a first bandwidth of a first carrier signal with respect to a second bandwidth of a second carrier signal such that the first bandwidth adjoins to or overlaps the second bandwidth, the first bandwidth being greater than the second bandwidth.
According to further refinements of the example of the present invention as defined under the above first aspect,                the method further comprises transmitting the first and second signals from a single means for transmitting;        the method further comprises transmitting the first and second signals from a plurality of means for transmitting in a coordinated manner.        
According to an example of the present invention, in a second aspect, this object is for example achieved by a method comprising:
transmitting a transmission signal comprising a plurality of subcarrier signals of a first carrier signal, each of which subcarrier signals being subtracted by an effective interference of a modulated second carrier signal.
According to further refinements of the example of the present invention as defined under the above second aspect,                the method further comprises, prior to the transmitting, subtracting the effective interference of the modulated second carrier signal from each of the plurality of subcarrier signals of the first carrier signal;        the method further comprises, prior to the transmitting, filtering the modulated second carrier signal for removing the subcarrier signals overlapping the modulated second carrier signal in bandwidth;        the method further comprises, after the subtracting and prior to the transmitting transforming a result signal resulting from the subtracting from frequency domain into time domain, inserting time intervals into the transformed result signal, and combining the result signal being transformed and inserted with time intervals with the filtered and modulated second carrier signal to form the transmission signal;        the method further comprises, after the filtering and prior to the subtracting, transforming the modulated first carrier signal from time domain into frequency domain;        the method further comprises, after the transforming, calculating, by filtering the transformed and modulated second carrier signal, a resulting distortion from the second carrier signal to the first carrier signal based on at least one of timing information and channel information.        
According to an example of the present invention, in a third aspect, this object is for example achieved by a method comprising:
retrieving a first carrier signal from a received transmission signal comprising a plurality of subcarrier signals of the first carrier signal, each of which subcarrier signals being interfered by an effective interference of a modulated second carrier signal.
According to further refinements of the example of the present invention as defined under the above third aspect,                the method further comprises, prior to the retrieving, receiving the transmission signal;        the retrieving is performed by subtracting a generated replica of the second carrier signal from the received transmission signal;        the method further comprises, prior to the subtracting, generating the replica of the second carrier signal by demodulating the decoded transmission signal, decoding the received transmission signal, and filtering the demodulated and decoded transmission signal for removing the subcarrier signals overlapping the modulated second carrier signal in bandwidth;        the retrieving further comprises, after the subtracting, transforming a signal resulting from the subtracting from time domain into frequency domain;        the method further comprises, after the receiving and prior to the retrieving, queuing (S3-1) the received transmission signal;        the retrieving is performed by decoding the received transmission signal, iltering the decoded transmission signal for removing the subcarrier signals overlapping the modulated second carrier signal in bandwidth, detecting a midamble in at least one signal burst of the second carrier signal based on a reference midamble, extracting the midamble from the current signal burst, estimating current channel information from the extracted midamble, and processing symbols sent via the first carrier signal based on the estimated current channel information during a subsequent burst of the second carrier signal after the at least one burst.        
According to an example of the present invention, in a fourth aspect, this object is for example achieved by a method comprising:
distributing, in unoccupied control channel elements of a first carrier signal having a first bandwidth, at least a portion of a second carrier signal having a second bandwidth by using different control channel configurations in at least one neighboring cell, the first bandwidth being greater than the second bandwidth.
According to further refinements of the example of the present invention as defined under the above first to fourth aspects,                the first carrier signal is a long term evolution carrier signal;        the second carrier signal is a global system for mobile communications carrier signal;        the transforming from time domain into frequency domain is one of a Fourier transformation and a fast Fourier transformation;        the transforming from frequency domain into time domain is one of an inverse Fourier transformation and an inverse fast Fourier transformation;        the timing information is an orthogonal frequency division multiplexing guard interval;        the channel information is channel state information;        the queuing is performed based on a first in first out queue.        
According to an example of the present invention, in a fifth aspect, this object is for example achieved by an apparatus comprising:
means for accommodating, in frequency domain, a first bandwidth of a first carrier signal with respect to a second bandwidth of a second carrier signal, the first bandwidth adjoining to or overlapping the second bandwidth, and the first bandwidth being greater than the second bandwidth.
According to further refinements of the example of the present invention as defined under the above fifth aspect,                the apparatus further comprises a single means for transmitting the first and second signals;        the apparatus further comprises a plurality of means for transmitting the first and second signals in a coordinated manner;        the or each means for transmitting is constituted by a radio frequency, power amplifier and antenna chain.        
According to an example of the present invention, in a sixth aspect, this object is for example achieved by an apparatus comprising:
means for transmitting a transmission signal comprising a plurality of subcarrier signals of a first carrier signal, each of which subcarrier signals being subtracted by an effective interference of a modulated second carrier signal.
According to further refinements of the example of the present invention as defined under the above sixth aspect,                the apparatus further comprises means for subtracting, prior to the transmitting performed by the means for transmitting, the effective interference of the modulated second carrier signal from each of the plurality of subcarrier signals of the first carrier signal;        the apparatus further comprises means for filtering, prior to the transmitting performed by the means for transmitting, the modulated second carrier signal for removing the subcarrier signals overlapping the modulated second carrier signal in bandwidth;        the apparatus further comprises means for transforming, after the subtracting performed by the means for subtracting and prior to the transmitting performed by the means for transmitting, a result signal resulting from the subtracting from frequency domain into time domain, means for inserting, after the subtracting performed by the means for subtracting and prior to the transmitting performed by the means for transmitting, time intervals into the transformed result signal, and means for combining, after the subtracting performed by the means for subtracting and prior to the transmitting performed by the means for transmitting, the result signal being transformed and inserted with time intervals with the filtered and modulated second carrier signal to form the transmission signal;        the apparatus further comprises means for transforming, after the filtering performed by the means for filtering and prior to the subtracting performed by the means for subtracting, the modulated first carrier signal from time domain into frequency domain;        the apparatus further comprises means for calculating, after the transforming performed by the means for transforming and by filtering the transformed and modulated second carrier signal, a resulting distortion from the second carrier signal to the first carrier signal based on at least one of timing information and channel information.        
According to an example of the present invention, in a seventh aspect, this object is for example achieved by an apparatus comprising:
means for retrieving a first carrier signal from a received transmission signal comprising a plurality of subcarrier signals of the first carrier signal, each of which subcarrier signals being interfered by an effective interference of a modulated second carrier signal.
According to further refinements of the example of the present invention as defined under the above seventh aspect,                the apparatus further comprises means for receiving the transmission signal prior to the retrieving performed by the means for retrieving;        the means for retrieving further comprises means for subtracting a generated replica of the second carrier signal from the received transmission signal;        the apparatus further comprises means for generating, prior to the subtracting performed by the means for subtracting, the replica of the second carrier signal, the means for generating comprising means for demodulating the decoded transmission signal, means for decoding the received transmission signal, and means for filtering the demodulated and decoded transmission signal for removing the subcarrier signals overlapping the modulated second carrier signal in bandwidth;        the means for retrieving further comprises means for transforming, after the subtracting performed by the means for subtracting, a signal output by the means for subtracting from time domain into frequency domain;        the apparatus further comprises means for queuing the received transmission signal after the receiving performed by the means for receiving and prior to the retrieving performed by the means for retrieving;        the means for retrieving comprises means for decoding the received transmission signal, means for filtering the decoded transmission signal for removing the subcarrier signals overlapping the modulated second carrier signal in bandwidth, means for detecting a midamble in at least one signal burst of the second carrier signal based on a reference midamble, means for extracting the midamble from the current signal burst, means for estimating current channel information from the extracted midamble, and means for processing symbols sent via the first carrier signal based on the estimated current channel information during a subsequent burst of the second carrier signal after the at least one burst.        
According to an example of the present invention, in an eighth aspect, this object is for example achieved by an apparatus comprising:
means for distributing, in unoccupied control channel elements of a first carrier signal having a first bandwidth, at least a portion of a second carrier signal having a second bandwidth by using different control channel configurations in at least one neighboring cell, the first bandwidth being greater than the second bandwidth.
According to further refinements of the example of the present invention as defined under the above fifth to eighth aspects,                the first carrier signal is a long term evolution carrier signal;        the second carrier signal is a global system for mobile communications carrier signal;        the transforming from time domain into frequency domain is one of a Fourier transformation and a fast Fourier transformation;        the transforming from frequency domain into time domain is one of an inverse Fourier transformation and an inverse fast Fourier transformation;        the timing information is an orthogonal frequency division multiplexing guard interval;        the channel information is channel state information;        the means for queuing is configured to queue based on a first in first out queue;        at least one, or more of means for accommodating, means for transmitting, means for subtracting, means for filtering, means for calculating, means for combining, means for transforming, means for inserting, means for retrieving, means for receiving, means for generating, means for queuing, means for modulating, means for demodulating, means for decoding, means for detecting, means for extracting, means for estimating, means for processing, means for distributing and the apparatus is implemented as a chipset or module.        
According to an example of the present invention, in a ninth aspect, this object is for example achieved by a system comprising:
a transmission apparatus according to the above sixth aspect;
an accommodating apparatus according to the above fifth aspect;
a receiving apparatus according to the above seventh aspect; and
a distributing apparatus according to the above eighth aspect.
According to an example of the present invention, in a tenth aspect, this object is for example achieved by a computer program product comprising code means for performing method steps of a method according to any one of the above first to fourth aspects, when run on a processing means or module.
In this connection, it has to be pointed out that examples of the present invention enable one or more of the following:                Alleviating a need for separation of the LTE spectrum into two or more different LTE carriers;        Alleviating a need for insertion of rather large (frequency) guard bands to separate LTE and GSM systems from each other;        Enhancing overall spectral efficiency of the system concept;        Complying with a legacy GSM receiver, since the interference due to the LTE signal is mainly blocked due to according receiver filters, and since the residual LTE out of band interference is very small;        Providing full GSM coverage;        Effectively combining LTE and GSM signals, such that specifically GSM might be included into the LTE signal at an arbitrary place of the spectrum, e.g. at suitable positions for reducing the interference on control channels.        Allowing support of UEs (user equipments) by pre-coding, which UEs are not aware of the combined LTE-GSM transmission. This may be facilitated by CSI (channel state information) that may be available;        Enabling interference cancellation in the UEs e.g. by implementing a GSM decoder. Additionally, corresponding control signals and messages are defined e.g. for broadcasting of the location of the GSM carrier.        